Arizona's Proposition 105 won't immediately change any taxes, but its implications for tax policy in the state are potentially severe. The question seeks to amend the state's constitution to require that any tax increase be approved by a majority of registered voters. This would be in addition to the requirement that tax increases enacted through the legislature be approved by 2/3 of legislators.
Under this new proposal, if, for example, only half of registered voters took the time to vote in an election where a tax increase was on the ballot, every single one of them would have to vote in approval of the tax measure for it to become law. Essentially, any registered voter that fails to vote will be counted as in opposition to the measure. As one observer puts it, "anyone who wants to vote no can just stay at home."
For some perspective, no ballot initiative (tax related or otherwise) has received approval from a majority of registered voters in Arizona since 1974. In fact, it's possible that at majority of registered voters do not even vote in some elections.
The passage of Proposition 105, coupled with the 2/3 majority requirement in the legislature, could perhaps bring to an end the possibility of any future tax increases occurring in Arizona. Needless to say, this would be a very irresponsible arrangement, given the recent budget troubles in the state.